The present invention generally relates to the field of disk drives and, more particularly, to sliders for disk drives which are designed to fly above a rigid magnetic recording disk of the disk drive during disk drive operations.
One way to characterize the manner in which information is recorded to and/or read from a rigid, magnetic, computer-readable storage medium (e.g., a disk) is the manner in which the magnetic recording head interfaces with the disk. Contact recording has at least been proposed to place the head and disk in direct physical contact when exchanging signals therebetween. Theoretically this maximizes the performance of the head and disk at least in relation to reading information from and writing information to the disk. Other issues have kept contact recording systems from realizing commercial success. Constant contact between the head and disk presents both wear and contamination (e.g., through generation of particulates) issues which need to be addressed by the disk drive design. Heat generated by the continuous contact between the head and disk during disk drive operations can also have an adverse effect on the accuracy of the exchange of information between the head and disk (e.g., via thermal transients or asperities). Frictional forces from the contact between the recording head and disk can also cause data transfer problems in the form of track misregistrations, as well as bit shift or jitter caused by suspension and/or air-bearing resonance excitations.
Another approach which has been utilized in commercial disk drive designs is for the magnetic recording head to fly above the surface of the rigid, magnetic disk. Typically the magnetic recording head includes a slider with a magnetic recording and/or writing element(s) carried thereby. One or more air-bearing surfaces are included on the lower surface of the slider which project at least generally toward the disk. These air-bearing surfaces are shaped/oriented on the slider body so that the boundary layer of air which is carried by the rigid disk during rotation thereof is compressed and forced to flow underneath the slider. Rotation of the disk in excess of a certain velocity will generate sufficient forces on the air bearing surfaces to lift the slider above the surface of the disk toward which the air-bearing surfaces at least generally project.
Relatively significant development efforts have been directed to the design of the air-bearing surfaces of sliders of the flying type. The problems which have been addressed by these efforts have not been simply to realize flying of the slider in spaced relation to the disk, but instead to considerations such as attempting to accurately control the fly height or to achieve a consistent fly height. Another area of focus has been to attempt to minimize the spacing between the head and disk during disk drive operations without actually having any significant contact which can have adverse effects on data transfer operations, as well as the operability of the disk drive or components thereof. Current state-of-the art, commercially available disk drives with MR/GMR heads operate with an average fly height of about 30 nanometers. However, this does not correspond with a 30 nanometer spacing between the magneto-resistive recording element and the disk. Pole-tip recession typically adds another 5-7 nanometers to the actual spacing being the recording element and the disk, as does the carbon overcoat which is typically included on the bottom surface of current flying sliders. Reducing the spacing between the flying head and rigid, rotating disk would be desirable to realize higher bit and track densities.
The present invention is generally directed to sliders which fly above a rotating, rigid computer-readable storage medium in a disk drive. Hereafter, this will be characterized as a xe2x80x9cdisk.xe2x80x9d More specifically, the present invention is generally directed to a flying slider having a wear pad which is disposed typically at least substantially adjacent to a trailing edge of the slider and which will typically carry the sensor(s) or transducer(s) which operatively interface with the disk to read and/or write information therefrom/thereto. This wear pad is burnished during the initial operation of the disk drive to create a small gap between the slider and the disk which is in effect customized to the disk drive at issue. Principles of the present invention may be used in both contact start/stop type disk drive designs, and well as in load/unload type disk drive designs.
A first aspect of the present invention is embodied in a method for operating a disk drive which includes a rigid disk and a slider. A wear pad is disposed on a lower surface of the slider or that surface which at least generally projects toward the disk. The method includes executing a first flying step which in turn includes flying the slider a distance above the disk which is no more than the glide height or within the glide avalanche of the disk. The term xe2x80x9cglide heightxe2x80x9d means a spacing between the disk and slider such that the slider contacts at least part of the disk (e.g., its upper surface roughness) during relative movement between the slider and disk (e.g., by rotation of the disk). While the slider is flying above the disk a distance which is no more than the glide height, the wear pad is burnished (e.g., material is removed from the wear pad). Burnishment of the wear pad is terminated and some time thereafter a second flying step is initiated, which may be immediately after the wear pad has been burnished to an appropriate degree. The slider thereafter flies above the disk a distance which is typically only slightly greater than the glide height during this second flying step such that the slider and disk remain in preferably constant spaced relation.
Various refinements exist of the features noted in relation to the subject first aspect of the present invention. Further features may also be incorporated in the subject first aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. The lower surface of the slider may include at least one air bearing surface and a lifting force may be exerted thereon by rotation of the disk. While the wear pad is being burnished, the lifting forces are insufficient to dispose the slider above the disk a distance which is in excess of the glide height. Once the wear pad has been burnished, however, the lifting forces exerted on the air bearing surface(s) of the slider are sufficient so as to dispose the slider above the disk a distance which is typically slightly in excess of the glide height. Stated another way, while the disk is being rotated at a certain velocity, the slider is maintained at substantially a constant distance above the disk. This distance is selected such that the wear pad will contact the disk and will be burnished by this contact and relative movement between the disk and wear pad. Sufficient burnishment of the wear pad will eventually create a typically small gap between the slider and the disk while the disk continues to be rotated at the same velocity. Burnishing the wear pad in this manner thereby provides a typically very small gap between the slider and disk, which in turn yields a fly height of significantly reduced magnitude in relation to the known prior art. In one embodiment, the fly height is no more than about 5-6 nanometers above the mean plane of the surface roughness of the disk (i.e., the 5-6 nanometers includes the glide avalanche). Another way of characterizing this significantly reduced fly is that the fly height in relation to the subject first aspect of the present invention is only slightly greater than the glide avalanche. By disposing the read and/or write sensor in the wear pad associated with this first aspect of the present invention, the spacing between the same and the disk is also thereby reduced which enhances the operative interface therebetween (e.g., the exchange of signals to read and/or write). This gap is also customized in that the lower extreme of the wear pad is burnished into a surface which is at least substantially co-planar with the disk while the slider is flying relative to the disk.
Preferably the wear pad of the subject first aspect of the present invention is not an air bearing surface such that the burnishment thereof does not have any affect on the fly height of the slider (e.g., no greater than about 1% of the lift forces exerted on the slider during disk drive operations may be attributed to the presence of the wear pad). Typically the wear pad will be disposed at least substantially at a xe2x80x9ctrailing edgexe2x80x9d of the slider as that term is commonly used in the art. Burnishment of the wear pad is desired, not the air bearing surfaces. This may be affected by disposing the slider at a relatively steep pitch relative to the disk during disk drive operations (e.g., at least about 150 microradians).
The transducer(s) or sensor(s) which is used to read and/or write information from/to the disk may be embedded within the slider before burnishment is undertaken in accordance with the subject first aspect of the present invention. That is, at least some wear pad material initially may be disposed between the sensor(s) and the disk. The method of the subject first aspect may further include burnishing the wear pad until there is no longer any wear pad material between the sensor(s) and the disk. Another way of characterizing this feature of the subject first aspect is that the wear pad is burnished so as to eventually expose the sensor(s) to the air gap which exists between the slider and disk during disk drive operations after what may be characterized as an initialization operation of sorts for the disk drive. Wear pad material may be burnished away in accordance with the foregoing, as well as an overcoat that is typically disposed on the lower surface of the slider at the completion of the manufacturing thereof.
Burnishment of the wear pad in accordance with the subject first aspect may be monitored in at least some respect. For instance, a read/write signal between the sensor(s) and the disk will include xe2x80x9cnoisexe2x80x9d or other xe2x80x9cspikesxe2x80x9d while there is contact between the slider and the disk. When the gap is defined between the slider and the disk by the subject burnishment, this xe2x80x9cnoisexe2x80x9d will no longer be evident in the signal between the sensor(s) and the disk. This may be used as an indication that the burnishing operation may be terminated. In this regard, the burnishment of the wear pad in accordance with the subject first aspect will typically be done at the manufacturer""s facilities. By monitoring the above-noted signal, the point in time when the gap is initially established between the entirety of slider and the disk may be identified such that the current operation may be terminated. Relatedly, after the wear pad has been burnished in accordance with the first aspect of the invention, the disk drive may be released for distribution (e.g., to consumers or end users), although other tests or the like may first need to be executed.
The burnishing operation of the subject first aspect may be executed rather expediently so as to not significantly add to the time required to prepare a disk drive for release for distribution to consumers. In one embodiment, a gap may be established between the slider and the disk in no more than about 60 minutes, and in another embodiment in no more than about 10 minutes. This fast burnishing may be facilitated by forming the wear pad from a relatively soft material in comparison to the air bearing surface(s) which are also disposed on the lower surface of the slider (e.g., the hardness of the portion of the slider which is the wear pad may have a smaller hardness value than those portions of the slider which define the air bearing surfaces). Appropriate materials for the wear pad include alumina, while appropriate materials for the air bearing surfaces used by the slider include ceramics such as a composition of alumina and titanium carbide.
A second aspect of the present invention is embodied in a method for operating a disk drive which includes a rigid disk and a slider. The slider includes at least one transducer which operatively interfaces with the disk to read and/or write information from/to the disk, as well as at least one air bearing surface and a wear pad which are disposed on a lower surface of the slider which at least generally projects toward the disk during disk drive operations. The method of the second aspect includes initializing the disk drive. Initialization of the disk drive includes rotating the disk relative to the slider and exerting a lifting force on the slider by the action of the air associated with the rotating disk on the air bearing surface(s) of the slider. During this initialization operation there is contact between the wear pad and the disk at least at some point in time. This contact and the relative movement between the disk and the slider burnishes the wear pad. Sufficient burnishment of the wear pad establishes a typically small gap between the slider and the disk, and thereafter there is no longer any substantial burnishment of the wear pad. That is, once the initialization operation is complete, there is no longer any substantial burnishment of the wear pad. At least one data transfer operation is executed after the disk drive has been initialized in accordance with the foregoing, although data transfer operations could be executed during the initialization procedure as well. Data transfer operations are affected by rotating the disk relative to the slider, maintaining a gap between the slider and a disk which again was provided by the burnishment of the wear pad in the initialization procedure, and exchanging at least one signal between at least one of the transducer(s) carried by the slider and the disk. The various features discussed above in relation to the first aspect of the present invention may be incorporated in this second aspect of the present invention as well, and in the manner noted above.
A third aspect of the present invention is embodied in a method for operating a disk drive which includes a rigid disk and a slider. The slider includes at least one transducer which operatively interfaces with the disk to read and/or write information from/to the disk, as well as at least one air bearing surface and a wear pad which are disposed on a lower surface of the slider which at least generally projects toward the disk during disk drive operations. Notably, this transducer is initially embedded within the wear pad. The method of the third aspect includes the steps of rotating the disk, burnishing the wear pad at least at some point in time during this rotation, exposing the noted transducer through this burnishing operation, and flying the slider relative to the disk during the rotation thereof. The exposure of the noted transducer means that there is no structural material between the transducer and disk. Stated another way, the transducer directly interfaces with the air gap between the slider and the disk. The various features discussed above in relation to the first aspect of the present invention may be incorporated in this third aspect of the present invention as well, and in the manner noted above.
A fourth aspect of the present invention is embodied in a slider for a disk drive which includes a rigid disk. The slider of the subject fourth aspect is of the xe2x80x9cflying type.xe2x80x9d In this regard, the slider includes a slider body which may be characterized as extending along a reference axis to define a longitudinal extent of the slider body. The slider body includes upper and lower surfaces, with the lower surface at least generally projecting toward the disk of the disk drive when installed therein. The slider body further includes a leading edge and trailing edge as those terms are commonly used in the art and which would be longitudinally spaced relative to the above-noted reference axis. Other portions of the slider body include a pair of sides which are laterally spaced relative to the above-noted reference axis and which extend longitudinally between the leading and trailing edges.
The lower surface of the slider of the subject fourth aspect is designed to have a significantly reduced fly height in comparison to the prior art, and which is typically only slightly more than the glide height as that term is commonly used in the art. In this regard, the lower surface includes a wear pad which is disposed at least substantially at the trailing edge of the slider body, at least one transducer which is carried by this wear pad, and an air bearing surface system (i.e., one or more air bearing surfaces). In one embodiment, the wear pad is separate from and is not part of the air bearing surface system. That is, rotation of the disk relative to the slider of the subject forth aspect of the present invention generates substantially no lifting forces on the slider through the noted wear pad.
Various refinements exist of the features noted in relation to the subject fourth aspect of the present invention. Further features may also be incorporated in the subject fourth aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. The wear pad of the fourth aspect is disposed at least substantially adjacent to the trailing edge of the slider body. In this regard and in one embodiment, the wear pad is disposed about 0.0004 inches from the trailing edge of the slider body. Preferably the wear pad is centrally disposed between the pair of laterally-spaced sides of the slider body. Portions of the lower surface of the slider body which surround the wear pad may be recessed in relation to the wear pad such that the wear pad extends further toward the disk then these adjacent portions (e.g., the wear pad may be characterized as an island of sorts). Relatedly, a recess may be disposed in front of the wear pad (i.e., in the direction of the leading edge of the slider body) and may be of a depth such that the wear pad does not function as an air bearing surface for the slider.
Characterization of the wear pad as such is not necessarily meant to functionally define the wear pad for all-time. Instead, the wear pad of the subject fourth aspect may indeed function as a wear pad between the slider and the disk during only an initial portion of disk drive operations and in a manner contemplated by the first, second, and third aspects noted above. That is, after an initial burnishing of the wear pad the first time the disk drive is operated, the function of the wear pad is effectively limited to being a carrier for the transducer(s) for operatively interfacing with the disk (e.,g., a structure on which the transducer(s) is mounted).
The air bearing surface system of the subject fourth aspect may include a first air bearing surface. This first air bearing surface may be disposed relatively close to the wear pad. In one embodiment, this first air bearing surface and the wear pad are separated by the above-noted recess which provides non-air bearing surface characteristics for the wear pad. Preferably the first air bearing surface and the wear pad are spaced by a distance of no more than about 0.010 inches, and in one embodiment are spaced by a distance of about 0.003 inches, as measured along a line which is parallel with the above-noted reference axis which again defines the longitudinal extent of the slider. Stated another way, the first air bearing surface and the wear pad are spaced by a distance which is within a range of about 5% to about 20% of the length of the slider. Another characterization of the xe2x80x9cclosenessxe2x80x9d of the noted first air bearing surface and the wear pad is that they may be characterized as being disposed on the same half of the slider body. xe2x80x9cHalfxe2x80x9d in this context is in relation to the longitudinal extent of the slider body, or the half-way point between the leading edge and trailing edge of the slider body. Therefore, in the subject characterization both the wear pad and the first air bearing surface would be disposed on that part of the lower surface of the slider body which extends from the trailing edge to the longitudinal midpoint of the slider body. Other air bearing surfaces may be disposed on this half as well and/or one or more air bearing surfaces may be disposed on the opposite half of the slider body as well (e.g., more toward the leading edge).